Copyright ©The Author(s) 2015. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Pharmacol. Mar 9, 2015; 4(1): 31-46
Published online Mar 9, 2015. doi: 10.5497/wjp.v4.i1.31
Antimicrobial resistance in clinically important biofilms
Fatemeh Rafii, Mark E Hart
Fatemeh Rafii, Mark E Hart, Division of Microbiology, National Center for Toxicological Research, FDA, Jefferson, AR 72079, United States
Author contributions: Both authors contributed to this work.
Conflict-of-interest: The authors declare no conflicts of interest regarding this manuscript.
Open-Access: This article is an open-access article which was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See:
Correspondence to: Fatemeh Rafii, Research Microbiologist, Division of Microbiology, National Center for Toxicological Research, FDA, Jefferson, AR 72079, United States.
Telephone: +1-870-5437342 Fax: +1-870-5437307
Received: September 24, 2014
Peer-review started: September 24, 2014
First decision: October 17, 2014
Revised: November 27, 2014
Accepted: December 16, 2014
Article in press: December 17, 2014
Published online: March 9, 2015

A biofilm contains a consortium of cohesive bacterial cells forming a complex structure that is a sedentary, but dynamic, community. Biofilms adhere on biotic and abiotic surfaces, including the surfaces of practically all medical devices. Biofilms are reported to be responsible for approximately 60% of nosocomial infections due to implanted medical devices, such as intravenous catheters, and they also cause other foreign-body infections and chronic infections. The presence of biofilm on a medical device may result in the infection of surrounding tissues and failure of the device, necessitating the removal and replacement of the device. Bacteria from biofilms formed on medical devices may be released and disperse, with the potential for the formation of new biofilms in other locations and the development of a systemic infection. Regardless of their location, bacteria in biofilms are tolerant of the activities of the immune system, antimicrobial agents, and antiseptics. Concentrations of antimicrobial agents sufficient to eradicate planktonic cells have no effect on the same microorganism in a biofilm. Depending on the microbial consortium or component of the biofilm that is involved, various combinations of factors have been suggested to explain the recalcitrant nature of biofilms toward killing by antibiotics. In this mini-review, some of the factors contributing to antimicrobial resistance in biofilms are discussed.

Keywords: Biofilm, Bacteria, Antimicrobial agent, Medical devices, Nosocomial infections, Resistance

Core tip: Biofilm formation on host tissues and medically implanted devices is a major health problem, and the infections caused by bacteria in biofilms are hard to treat with antimicrobial agents. They are the cause of frequent and recurrent infections after the termination of antimicrobial treatments. The reasons for the recalcitrant nature of biofilms to antimicrobial treatment are varied and have been attributed to different factors, including impermeability of biofilms, slow rates of growth and metabolic activity, and the presence of small colonies and persisters. They have been the subject of many investigations that will be discussed in this minireview.